Flextime rhymes with:
christmastime, pastime, peacetime, airtime, alltime, anytime, bedtime, centime, christmastime, daytime, dinnertime, downtime, everytime, fulltime, funtime, halftime, lifetime, longtime, lunchtime, maritime, mealtime, meantime, movietime, nighttime, noontime, overtime, parttime, pastime, peacetime, primetime, quicktime, ragtime, schooltime, showtime, sometime, springtime, summertime, wartime, wintertime
Flextime sounds like:
flagstone, fluctuation, folkstone